1. Field of the Invention
The present invention relates to a regenerating device for an optical recording medium, and more particularly, to a regenerating device using a two-dimensional image sensor as a detector for detecting signals.
2. Description of the Related Art Statement
Related art will be described with specific reference to FIGS. 1 to 5.
In a regenerating device for an optical recording medium which reads out information from an optical recording medium such as an optical disk, a photomagnetic disk, an optical card, a light source irradiates the optical recording medium (hereinafter defined as a medium) to obtain a reflected light beam; a photoelectric conversion of the reflected light beam obtained from the surface of the recording medium by means of non-stack-type detector such as a silicon photo-diode is performed; and signal processing is applied to the converted electric signal to enable the readout of data. Maintaining the focus of the optical beam for reading out the data and following-up a track can be performed by creating an error signal from the detected signal of the detector and by conducting feed-back to the optical head. FIG. 1 shows an example of a format of the medium. In the example, both a data pit 51 and a clock pit 52 are recorded, and the format of the medium is configured by sixteen data lines which are divided by a clock line 53 into two groups each consisting of eight lines, and these two groups are disposed in a upper and lower region as viewed in FIG. 1. In a reading process, sixteen data in each column are confirmed by one clock edge. Reference numeral 54 indicates a light spot of the beam for reading out.
FIG. 2 shows a detector for detecting under the condition in which the surface of the recording medium is projected as shown in FIG. 1. In the data pit 51, the high and low levels of a reflection factor is represented by "1" and "0", respectively. The data is detected by data cells 55, sixteen of which are vertically disposed as viewed in FIG. 2. Four clock-cell groups 56 perform to detect a clock. Each edge of the clock signal regenerated by the cell group 56 is a confirmed timing for the data cell. The clock-cell group 56 configures a pair by two cells.
FIG. 3 shows an optical head 60 and a detecting system.
In the optical head 60 shown in FIG. 3, a light beam emitted from a light source 61, which is a light-emitting diode (LED), is made to be a parallel light by means of a collimator lens 62. The light beam emitted from the light source 61 through the collimator lens 62 passes through a beam splitter 63 and then, through an objective lens 64, is irradiated onto a recording medium 65. The reflected light from the recording medium 65 passes through the objective lens 64 and reflected by the beam splitter 63, and then passes through an image-forming lens 66 to be led to a detector 67. As a result, the image-forming lens 66 projects an image of the medium on the detector 67. The detector 67 comprises sixteen data cells 55, four clock-cell groups 56, and servo cells C1 through C4 and D1 through D4 as shown in FIG. 2. A tracking actuator 68 is employed to control the light spot 54 on the surface of the detector 67 so that the light spot 54 does not move perpendicularly to the track of the medium by allowing the objective lens 64 to travel perpendicularly to the track of the medium. A focusing actuator 69 is employed to focus the light spot 54 by allowing the objective lens 64 to travel perpendicularly to the surface of the recording medium 65.
As shown in FIG. 2, in the focussed condition, the cells C1 through C4 are situated outside of a foot (edge) of the light spot 54, and the cells D1 through D4 are situated inside of the foot of the light spot 54.
As shown in FIG. 3, the detecting system of the device comprises: a servo cell I/V converting circuit 70 which converts the output currents of the cells C1 through C4 and the cells D1 through D4 to their voltages; a tracking error (TE) signal-generating circuit 71 to which the voltage signals from the servo cell I/V converting circuit 70 are inputted; a track (Tr) drive circuit 72; a focus error signal-generating circuit 73 to which the voltage signals from the servo cell I/V converting circuit 70 are inputted; and a focus (Of) drive circuit 74. The detecting system comprises: a read I/V conversion circuit 75 which converts the output currents (read signals) of the read cell groups 55 to their voltages; a binary circuit 76 which converts the read signal, which is converted into voltage, into a binary value; and a reading circuit 77 which executes data reading by binary valued read signals and clock signals (not illustrated).
The operation of the device is described as follows.
The detection of the focus location is enabled by detecting a variation of the diameter of a light beam on the surface of the detector. Therefore, the focus location is maintained by applying feed-back to the focus-error signal generating circuit 73 in the focussed condition so as to make the difference of the cells disposed in the foot of the beam shown in FIG. 2 zero. More specifically, maintaining the focus is achieved by applying a feed-back error signal to the focus drive actuator, wherein the error signal is calculated as the difference (.SIGMA. C-.SIGMA. D) between the sum of signals of the cells C1 to C4, which is represented as .SIGMA. C, and the sum of the signals of the cells D1 to D4, which is represented as .SIGMA. D. FIG. 4 is a practical example of a focus-error signal-generating circuit 73.
When the control is performed precisely in the tracking direction, the clock pit 52 is equally shared both by D1 and D2. The same situation can be applied to the cells D3 and D4. Accordingly, tracking servo is performed by making an error signal, which is represented by the equation of (D1+D3)-(D2+D4), and by feed-back of the error signal into the tracking drive actuator 68. FIG. 5 shows a practical example of the tracking error signal-generating circuit 71.
To perform data reading, the clock signal must be generated. The generation of the clock signal can be obtained by converting the difference between the sum of the clock cells 56 disposed in the consecutive even order and the sum of these cells 56 disposed in the consecutive odd order into a binary value. Then, each of the sixteen data is converted into a binary value and sampled at each edge of the leading and trailing of the clock to become confirmed data. At this time, the data has been modulated after the interleaving by being added by the correction bit, thus a demodulation, de-interleaving, and the error correction can be performed to the data and the reading is completed.
However, in the detector of the above described related art, there exists a restriction in that an overlapping of each cell was not allowed when conducting the tracking servo, the focus servo, the data reading, and in conducting clock generation respectively. Therefore, there was a restriction in the shape and the disposition of these cells. For instance, when the detecting region of the cell groups D1 through D4, as shown in FIG. 2, were to be extended, it was impossible due to the interference of the clock cell groups 56, and the region which may be shared in the view point of effectiveness could not be shared. There has been a problem that the required sensitivity of the respective output signals, such as focus servo, could not be sufficiently obtained because the detecting region could not be extended. Furthermore, because the shape and the disposition of each cell group is fixed for the recording medium having a different format, one device, or one optical head and the detecting system, could not function with a plurality of recording media having different formats.